textproduct: Rapid City

KEY MESSAGES

- Cooler and unsettled through the weekend with several rounds of precipitation and the potential for snow accumulations over the higher elevations

- Temperatures expected to remain at or below normal for the forecast period

UPDATE

Issued at 949 PM MDT Thu Apr 23 2026

03z surface analysis had snaking frontal boundary from southern NE through WY into northern ID. Water vapour loop had upper low spinning over southern SK with a nice-looking wave over ID/western WY propelled by 90kt jet streak. Lift ahead of this jet streak combining with low level frontogenesis north of frontal boundary to produce a blob of precipitation of northeastern WY southwestern SD per latest regional radar loop. Activity well- defined per infrared loop with localized moderate snow earlier this evening per KGCC observation. Even some weak convection just south of the CWA per GLM. Latest 00z guidance (especially the first 24-hours of the HREF) has upped QPF amounts, so have adjusted QPF through Friday night to account, but didn't go full bore given evidence of some convective contamination elements. This means a few inches of snow over the higher Black Hills, but once daybreak hits, it'll be much harder to accumulate on the roads. In addition, initial wave will be east of the CWA, but secondary wave will zoom through the CWA likely focusing on far southern SD. Finally, bigger wave shows up for Saturday night/Sunday with potential for beneficial QPF over southeast 3/5ths of the CWA.

Forecast update tonight takes these thoughts into account.

DISCUSSION

(This Evening Through Thursday) Issued at 1221 PM MDT Thu Apr 23 2026

Current upper air models and Water Vapor show the upper low over southern AB this afternoon, with a wave traversing the Dakotas. Surface analysis has a surface low over southern MB, with the current frontal boundary affecting our region 2/3 through the forecast area, currently stretching from north central SD down into southwestern SD, with a line of precipitation along it. Gusty northwest winds both ahead and behind the frontal boundary, with temperatures currently in the 30s and 40s behind the front, and 50s to near 70 out ahead of the front in south central SD.

Frontal boundary will exit the forecast area this afternoon moving eastward, with most areas seeing dry conditions the remainder of the day outside of the precip along the boundary. Gusty northwest winds will also begin diminishing late afternoon as pressure changes weaken farther behind the front. High Wind Warning and Wind Advisory remain in effect until early this evening, but may end up downgrading the High Wind Warning this afternoon as wind trends have been more in the 40 to 55 mph range.

This unsettled pattern continues for much of the forecast period, as the Upper Low slowly progresses from southwestern to south- central Canada, and models showing multiple waves rotating around the Low. Tonight into Friday will see another round of precipitation as a second disturbance pushes through, bringing isolated to scattered rain/snow. Could see some areas get some wetting precip with HREF 24 hr precip >= 0.25" showing a 40-60 percent signal for northeastern WY into the Black Hills and southwestern SD. Some of the higher elevation areas could see accumulations of an inch or two through Friday, though likely melting as it falls given the time of year.

Very little change to the pattern through the weekend, with the upper low mostly stationary, and disturbances bringing daily chances for light precipitation. Upper Low finally lifts northeast early next week but upper trough continues the cooler temps and unsettled weather through the forecast period.

AVIATION

(For the 06Z TAFS Through 06Z Friday Night) Issued At 1035 PM MDT Thu Apr 23 2026

A disturbance rotating through WY/eastern MT will continue to spread an area of precipitation across northeastern WY into the Black Hills/southwestern SD tonight. All snow is expected at KGCC, with rain initially for an hour or two at KRAP trending quickly to snow as the lower-levels saturate and cool. Expect areas of MVFR/IFR cigs/vsbys with the precipitation/low clouds overnight. The best chance of IFR to borderline LIFR conditions will focus on KGCC over the next several hours. Little change is expected Friday with periods of snow showers for much of the day, mixing again with rain at KRAP during the afternoon. We may see one or two 2-3 hour breaks Friday during which cigs may try to nudge back toward VFR and vsbys will be good, but agreement in when these breaks might occur is low across the guidance including the 00z HREF suite of CAMs. For now, will advertise -SHSN and -SHRASN through 21-22z/3-4pm, when agreement starts to increase that precipitation should be ending from west to east, along with improving cigs.

UNR WATCHES/WARNINGS/ADVISORIES

SD...None. WY...None.